JP2003132353A - Center line generator - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a center line generator automatically extracting a center line between boundary lines by forming Voronoi polygons on the basis of boundary line data representing a road or the like. SOLUTION: The center line generator has a computer execute a step of generating a plurality of points having a predetermined interval conforming to a set threshold on each of a plurality of boundary lines arranged separatively from each other on the basis of boundary lines of graphic vector data of a road or the like, a step of carrying out Voronoi tessellation to the plurality of points and forming Voronoi polygons, and a step of determining an outline acquired by coupling a plurality of the Voronoi polygons crossing a boundary line per boundary line as the center line between the boundary line and the other boundary line facing the boundary line. The predetermined interval is set at half or less of a shortest distance of separation distances between the boundary lines.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a centerline generation program executed by a computer for automatically generating centerlines between boundary lines, and more particularly to forming Voronoi polygons based on boundary line data representing roads and the like. The present invention relates to a centerline generation program that generates a centerline by

[0002]

2. Description of the Related Art In the past, when managing roads, rivers, waterways, etc., it was often necessary to determine where the centerline of them was.

In order to manage such roads and the like, line positions have been created at approximately the center of the width of the roads or the like, or have been formed into a network structure in consideration of the connection relationship of these lines. . However, in these formations, since it is mainly used at a small scale (1/10000 or less), it was done from the viewpoint that a single line (two lines if the boundary is converted into data) is sufficient for roads and the like. It is a thing. Here, the center line is usually adopted as a single line representing a roadside or the like. However, the center line is about the center, and its positional accuracy is low.

On the other hand, for large scales with high positional accuracy, the boundary line is converted into data, but the center line is not converted into data. this is,
Because the purpose of use is different from the small scale.

By the way, a map on which roads and the like are posted is often used as a paper medium. On the other hand, with the evolution of computer-based technology,
In order to improve the convenience of handling, a map has been scanned and imaged, or digitized for more advanced use, and has been used as vector data including polygonization.

[0006] Looking at these data conversion methods and the usage forms at small scales or large scales, the imaging method is used for small scales, and the vectorization method is used for large scales. Tend to be. This is because there are many maps at a large scale, and
Since the information density per sheet is low and it is not efficient, etc., the method by imaging is used less, and conversely, it is highly accurate, and moreover, it can withstand reuse and processing, so that vector The method by computerization has been widely used.

Here, as shown below, there are various methods for creating the center line data. (1) The position considered to correspond to the center line is written on the paper map, and in some cases it is written by the naked eye and directly generated from the paper map by digitizing. (2) The image obtained by scanning the paper map is directly subjected to thinning processing and is generated by raster / vector conversion. (3) It is generated by connecting the midpoints from the boundary line vector data. (4) Generated by combining the boundary line vector data and digitizing. (5) A combination of the midpoint connection of the boundary line vector data and the thinning process.

[0008]

As described above, there are various methods of creating centerline data. In recent years, there is an increasing need for highly accurate centerline vector data, particularly networked data, as is found in, for example, car navigation systems.

However, in dealing with such a situation, there are problems in each of the above methods, as will be described below. The method (1) is not so accurate and takes much effort even on a large-scale map, and it is also friendly.
The method (2) has a problem in accuracy. In the first place, the thinning process itself is heavy and time-consuming. The method (3) has a problem that the curve of a road or the like is distorted and the vehicle is discontinued at an intersection. The method (4) is a CAD system in which the boundary line is regarded as a rail, and the digital cursor is guided so as to be located at the midpoint, and it cannot be handled at intersections and sudden changes in width. In the method (5), when there is polygon data whose boundary is a road or the like, or when polygon data is created, the inside of the polygon is filled and then image / thin line processing is performed by vector / raster conversion. And
Raster / vector conversion is applied to the obtained centerline image to vectorize it. In a paper map, this is usually a display of only the border line, such as edging without painting the inside of the road with one color, because of a device on the map (map representation) for each road type. This is to avoid the problem that thinning processing cannot be performed directly in many cases.

Therefore, the present invention has been made in view of solving each of the problems as described above, and although it is highly accurate and abundant in the world, it has a boundary line and lacks a center line. The present invention aims to further utilize existing vector data by automatically generating center line data at high speed with respect to vector data.

Therefore, according to the present invention, the center line is generated by forming the Voronoi polygons related to the boundary line so that the center line necessary for managing roads, rivers and waterways can be easily determined. It is an object of the present invention to provide a centerline generation program for causing a computer that can automate the above.

[0012]

In order to solve the above-mentioned problems, in the present invention, in a centerline generation program for generating centerlines between boundary lines, each of them on a plurality of boundary lines arranged apart from each other. A step of generating a plurality of points having a predetermined interval in, a step of performing Voronoi division on the plurality of points to form a Voronoi polygon polygon,
For each of the boundary lines, an outline obtained by combining the plurality of Voronoi polygonal polygons intersecting the boundary line is defined as a center line between the boundary line and another boundary line facing the boundary line. The steps to perform are to be executed by the computer.

The predetermined interval is set to be equal to or less than ½ of the shortest distance among the separation distances of the boundary line,
The vertices forming the outline are thinned out to linearize along the boundary line.

The boundary line is defined by road graphic vector data or river / waterway graphic vector data.

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION Next, regarding a center line generation program for causing a computer to automatically generate a center line according to the present invention, an example of automatically obtaining a center line on a road in a map will be described. The embodiment will be described.

In the present invention, attention has been paid to the fact that the center position of the boundary of a road or the like having an arbitrary width including the intersection is a position where the power from the boundary line forming the road opposes.

Here, there is a Voronoi division method as a method of dividing the space into points of influence. Voronoi division is a method that, when multiple points are given in the space, classifies each point in the space according to which point is closest and divides the space into the influence zones related to each point. Is formed by a polygon (Voronoi polygon). The line of the polygon is a position where the forces of adjacent points oppose each other, and each side forming the polygon has a characteristic that it is a part of a bisector between two points.

By using this method, a plurality of points at appropriate intervals are arranged on the boundary line forming the road, and each point is used as a point for Voronoi division to approximate the power of the road boundary line, By selecting the side located between the respective boundary lines among the respective sides of the formed Voronoi polygon, a line at which the powers of the boundary lines oppose each other, that is, a center line is generated.

Therefore, referring to the drawings, a centerline generation program that can automatically generate a centerline of a road in a road map based on the centerline generation method by forming this Voronoi polygon is applied. The system will be described.

FIG. 1 shows an outline of a system to which the centerline generation program according to this embodiment is applied.

The center line generation system comprises a control unit 1, a storage unit 2, an operation unit 3, a display unit 4, and a printing unit 5. The control unit 1 is a computer that controls the entire system, and includes a boundary line acquisition unit 11, a point generation unit 12, a polygon division formation unit 13, a polygon selection / connection unit 14, a polygon outline extraction unit 15, and It has functional parts such as the center line output part 16. The computer including the control unit 1 may be a stand-alone computer or a client terminal connected to a network such as a LAN.

A map is stored in the storage unit 2, and at least graphic vector data relating to the boundary line of the road is stored. Further, the graphic vector data on the road center line extracted by the control unit 1 is stored. Operation part 3
Is used by the operator to input or instruct information necessary for processing in the control unit 1. The display unit 4 displays information necessary for processing by the control unit 1,
Alternatively, the graphic vector data of the road, the graphic vector data of the extraction result, and the like are displayed, and the printing unit 5 outputs a hard copy of these graphic vector data.

The operation processing of the centerline generation program according to the present embodiment applied to the system configuration as described above will be described with reference to the processing flow of FIG. 2 and the image examples shown in FIGS. Here, each of the image examples shown in FIGS. 3 to 5 does not need to be displayed on the display unit 4, and is shown as an image for convenience of explaining the processing situation in an easy-to-understand manner. There is also.

First, the operation unit 3 is operated to move the center line of the road.
Specify the prescribed area that needs to be extracted and acquire the boundary line
By the section 11, the area stored in the storage section 2
Road figure vector data is read (step S1).
Display the read road figure vector data of the area
When displayed as an image in the section 4, the image X in FIG.
₁₁become that way. The solid lines in the figure represent the boundaries of the road.
And the boundary line is L₁, L_Two, L_ThreeIndicated by. image
X₁₁Then, the road shape of the T-junction is shown, and the boundary line L₁Is
Point p₁Bend at and line segment L₁₁And L₁₂Consists of a boundary
Line L_TwoIs the point p_TwoBend at and line segment L₂₁And L₂₂So
And then the boundary line L_ThreeIs the point p_ThreeBends slightly at line segment L
₃₁And L₃₂It is composed of.

Here, when the graphic vector data of the desired predetermined area is obtained and the image is displayed, the operation unit 3 is operated to set a plurality of points at predetermined intervals on the line segment forming the boundary line. The threshold value for generating is set (step S2). This threshold may be set in advance.

Next, when this threshold value is set, the point generator 12 generates a plurality of points so that the distance between points on the boundary line is within the threshold value. _On the line segment L ₁₁ of the boundary line L ₁ , a plurality of points p are arranged at predetermined intervals on a line other than the point p _1.
11m , and a plurality of points p _12m are generated at predetermined intervals on a line other than the point p ₁ on the line segment L ₁₂ . Similarly, with respect to the boundary line L ₂ , a plurality of points p _21l and p
_22l and a plurality of points p on the boundary line L _3.
31n and a point p _32n are generated respectively (step S
3). The situation in which these multiple points are generated is as in the image X ₁₂ shown in FIG. In the figure, a plurality of points are indicated by black dots, and a plurality of points are indicated by l, m, and n.
Is typically shown by a subscript. Image X _{12 in} FIG. 3B
Shows a case where the predetermined interval of points is constant in any of the line segments of the boundary lines L ₁ , L ₂ and L ₃ . Then, this predetermined interval can be changed by changing the threshold value according to the shape, width, etc. of the road.

When these plural points are generated on the boundary line, the polygon division forming unit 13 forms a Voronoi polygon for the plural points on the boundary line (step S4).
This Voronoi polygon is a polygon having a shape obtained by dividing an area into two areas between adjacent points based on a plurality of points.
The plurality of points p ₁ , p _11m , and p ₁ shown in FIG.
_{2m, p 2, p 21l,} p 22l, p 3, p 31n, and _the state that created the Voronoi polygon with respect to _{p 32n,} shown as an image _{X 13} in (c) of FIG. For example,
The Voronoi polygon for the point p _11m is the polygon P
_11m , and the Voronoi polygon for the point p _{22 l} is
The polygon P _{22l is formed} , and the Voronoi polygon for the point p _31n is formed like the polygon P _31n .

Therefore, in order to generate the desired center line of the road, the polygon selecting / connecting unit 14 needs only polygons of Voronoi polygons for a plurality of points on the boundary line of the road. Select the Voronoi polygon formed at the position that intersects the road boundary line,
They are combined (step S5). This state is shown in FIG.
The image X ₁₄ in (d) is shown. In the same figure, the connection state is indicated by diagonal lines, and Voronoi polygonal polygons P _31n and P _32n are connected to a plurality of points p ₃ , p _31n and p _{32n with} respect to the boundary line L ₃ .

Next, in the polygon outline extraction unit 15,
Polygons connected as shown by the diagonal lines in (d) of 4
For, the outline of multiple polygons is extracted (
Step S6). The appearance of the outline being extracted in (e) of FIG.
The image X₁₅Indicated as. Shown with diagonal lines in (d) of FIG.
The polygons that have been_ThreeLine segment L₃₁And L
₃₂Is it formed for multiple points above
, These polygons are line segments L₁₁And line segment L₂₂Up
Since it is formed by relating to multiple points of
Outline C formed by the drawn polygon₁₁And C_ThirteenIs the way
It is the center line of the road. Furthermore, the line segment L of the boundary line₁₂
And line segment L₂₁Either line segment is acceptable between and
Minute L₁₂Or line segment L₂₁Voronoi polygonal po
A contour line C obtained by joining the ligons
₁₂Is also the road center line.

Even at the intersection of the T-junction as shown in FIG. 3 (a), the points p ₁ , p ₂ and p constituting the intersection are formed.
_{Since 31n} will be involved in the formation of Voronoi polygons, it was difficult to visually determine the centerline within the intersection, but the bisector between these points should be automatically the centerline. You can

Here, the image X shown in FIG.
_{As shown in 15} , when a plurality of points are generated on the boundary line and the two points that oppose each other are divided by the polygonal polygon, if the two points are deviated in the direction of the road boundary line, the two points are separated. The bisector that divides is not necessarily parallel to the road boundary line. Therefore, the contour line extracted in step S6 has a zigzag shape.

The center line output unit 16 can output the contour line shown in the image X ₁₅ as the center line of the road and display the image on the display unit 4. Further, the printing unit 5 makes a hard copy of this image. You can also do it. Alternatively, in the center line output unit 16, in order to make the zigzag shape presented by the contour line a smooth line corresponding to the road boundary line, the vertexes on the contour line may be thinned. The image X _15, the extracted outline images X ₁₆ in the state in which the smoothing process of a line along the road boundary line of FIG. 5 (f)
It was shown to. By performing the process of thinning out unnecessary vertices in this way, the amount of data can be reduced, and a center line that is visually pleasing can be created.

The threshold value set in step S2 must be less than or equal to one half of the road where the demobilization of the road in the area where the center line is to be generated is minimum. When creating a Voronoi polygon, it is possible to extract a good centerline if the points on the opposite lines are located almost vertically, but on any road, the points that are opposite are almost vertical. It's difficult to do. Therefore, the threshold may be set to at least ½ or less of the width of the narrowest road. In particular, at the intersection where the roads intersect, the intersection of the center line itself must be within the road.

As described above, the procedure for extracting the road center line by forming Voronoi polygon polygons for a plurality of points generated on the road boundary line based on the road graphic vector data , A simple concrete example such as the T-junction shown in (a) of FIG. 3 was described. Next, as shown in the image X ₂₁ of (a) of FIG.
It will be described that the centerline generation program according to the present embodiment can be executed even for graphic vector data having a complicated road shape. The procedure for executing this program and performing the extraction processing is the same as the processing flow shown in FIG.

First, when the road graphic vector data shown in the image X ₂₁ is fetched, the road L _N having the narrowest width is selected from among the roads shown in the image, and the threshold V
_th is a value corresponding to one half or less of the width of the road,
For example, road width if 5 _m, is set as _{V t} h = 2 (step S2). Then, the threshold value V _th is applied to generate a plurality of points on the road boundary line. Voronoi division is performed on the generated plurality of points to form a Voronoi polygonal polygon along the road boundary line (step S4). The state of formation of these polygons is shown in FIG.
Is shown as image X ₂₂ .

Then, the polygons formed side by side on the boundary line are combined to form one polygon, and the contour line C ₁ formed by each polygon is extracted (step S6). When the extracted outline and the road boundary are overlapped and displayed, an image X23 in FIG. 7C is obtained. Further, as shown in the image X ₂₄ of (d) of FIG. 7, a center line C ₂ obtained by straightening the contour line along the road boundary line can be obtained by appropriately thinning out the vertices of the contour line. it can.

In this way, the road center line can be easily extracted even based on the graphic vector data of the district having a complicated intersection, and the center line network can be easily formed without human intervention. , A proper centerline is obtained.

[0038]

According to the present invention, a plurality of points are generated in graphic vector data relating to a road, etc., Voronoi division is performed according to the plurality of points to form a polygon polygon, and an outline line formed by these polygons is formed. Since it is extracted as the road center line, the center line network will not be interrupted,
Appropriate centerlines can be drawn between road boundaries. Moreover, compared to the conventional centerline generation method, automatic and high-speed processing becomes possible.

Further, even when the map data of the area where the center line of the road or the like is to be obtained is an image, the boundary line is extracted from this image by edge extraction processing or the like, and raster / vector conversion is performed. If the boundary line vector is created, the center line can be easily obtained by applying the center line generation method of the present invention.

[Brief description of drawings]

FIG. 1 is a diagram illustrating general functional blocks of a system in which a centerline generation program according to the present invention is executed.

FIG. 2 is a diagram illustrating a processing flow by a functional block shown in FIG.

FIG. 3 is a diagram illustrating a state in which points are generated on a boundary line.

FIG. 4 is a diagram illustrating a state where the formed Voronoi polygons are combined along a boundary line.

FIG. 5 is a diagram illustrating a state in which a center line is extracted.

FIG. 6 is a diagram illustrating a state in which a Voronoi polygonal polygon is formed for a road figure having a complicated boundary line.

7 is a diagram illustrating a state in which a road center line is extracted from the road figure shown in FIG.

[Explanation of symbols]

1 ... Control unit 11 ... Boundary line acquisition unit 12 ... Point generation unit 13 ... Polygon division forming unit 14 ... Polygon selection / connection section 15 ... Polygon outline extraction unit 16 ... Center line output section 2 ... memory 3 ... Operation part 4 ... Display 5 ... Printing department

Claims (5)

[Claims] 1. A step of generating a plurality of points having a predetermined interval on each of a plurality of boundary lines arranged apart from each other, and Voronoi division of the plurality of points to form a Voronoi polygon polygon. And a contour line obtained by combining a plurality of Voronoi polygonal polygons that intersect the boundary line for each boundary line, between the boundary line and another boundary line facing the boundary line. A centerline generation program that causes a computer to execute a step of setting a centerline and generate a centerline between boundaries. 2. The center line generation program according to claim 1, wherein the predetermined interval is set to be equal to or less than ½ of the shortest distance among the separation distances of the boundary lines. 3. The center line generation program according to claim 1, wherein straightening is performed along the boundary line by thinning out vertices forming the outline. 4. The center line generation program according to claim 1, wherein the boundary line is based on road graphic vector data. 5. The centerline generation program according to claim 1, wherein the boundary line is based on river / waterway graphic vector data.